You're right that you can use the Karma booster from the BLTC, and the guild banner. There's also a guild karma boost (15% for 72 hours I think, maybe 48 hours). As well as this, if you go to one of the WvW maps, when your server are Out Manned or whatever it's called, meaning your server has almost no one there, you get another boost to your karma.

So with those 4 boosts you pretty much double the amount you get from the jugs.